Enhancing reliability with Latin Square redundancy on desktop grids.

Computational grids are some of the largest computer systems in existence today. Unfortunately they are also, in many cases, the least reliable. This research examines the use of redundancy with permutation as a method of improving reliability in computational grid applications. Three primary avenues are explored - development of a new redundancy model, the Replication and Permutation Paradigm (RPP) for computational grids, development of grid simulation software for testing RPP against other redundancy methods and, finally, running a program on a live grid using RPP. An important part of RPP involves distributing data and tasks across the grid in Latin Square fashion. Two theorems and subsequent proofs regarding Latin Squares are developed. The theorems describe the changing position of symbols between the rows of a standard Latin Square. When a symbol is missing because a column is removed the theorems provide a basis for determining the next row and column where the missing symbol can be found. Interesting in their own right, the theorems have implications for redundancy. In terms of the redundancy model, the theorems allow one to state the maximum makespan in the face of missing computational hosts when using Latin Square redundancy. The simulator software was developed and used to compare different data and task distribution schemes on a simulated grid. The software clearly showed the advantage of running RPP, which resulted in faster completion times in the face of computational host failures. The Latin Square method also fails gracefully in that jobs complete with massive node failure while increasing makespan. Finally an Inductive Logic Program (ILP) for pharmacophore search was executed, using a Latin Square redundancy methodology, on a Condor grid in the Dahlem Lab at the University of Louisville Speed School of Engineering. All jobs completed, even in the face of large numbers of randomly generated computational host failures

Resource Allocation in Vehicular Cloud Computing

Recently, we have witnessed the emergence of Cloud Computing, a paradigm shift adopted by information technology (IT) companies with a large installed infrastructure base that often goes under-utilized. The unmistakable appeal of cloud computing is that it provides scalable access to computing resources and to a multitude of IT services. Cloud computing and cloud IT services have seen and continue to see a phenomenal adoption rate around the world. Recently, Professor Olariu and his coworkers through series of research introduced a new concept, Vehicular Cloud Computing. A Vehicular Cloud (VC) is a network of vehicles in a parking lot that can provide computation services to users. In this model each vehicle is a computation node. Some of the applications of a VC include a datacenter at the airport, a data cloud in a parking lot, and a datacenter at the mall. The defining difference between vehicular and conventional clouds lies in the distributed ownership and, consequently, the unpredictable availability of computational resources. As cars enter and leave the parking lot, new computational resources become available while others depart, creating a dynamic environment where the task of efficiently assigning jobs to cars becomes very challenging. Our main contribution is a number of scheduling and fault-tolerant job assignment strategies, based on redundancy, that mitigate the effect of resource volatility in vehicular clouds. We offer a theoretical analysis of the expected job completion time in the case where cars do not leave during a checkpoint operation and also in the case where cars may leave while checkpointing is in progress, leading to system failure. A comprehensive set of simulations have shown that our theoretical predictions are accurate. We considered two different environments for scheduling strategy: deterministic and stochastic. In a deterministic environment the arrival and departure of cars are known. This scenario is for environments like universities where employees should be present at work with known schedules and the university rents out its employees\u27 cars as computation nodes to provide services as a vehicular cloud. We presented a scheduling model for a vehicular cloud based on mixed integer linear programming. This work investigates a job scheduling problem involving non-preemptive tasks with known processing time where job migration is allowed. Assigning a job to resources is valid if the job has been executed fully and continuously (no interruption). A job cannot be executed in parallel. In our approach, the determination of an optimal job schedule can be formulated as maximizing the utilization of VC and minimizing the number of job migrations. Utilization can be calculated as a time period that vehicles have been used as computation resources. For dynamic environment in terms of resource availability, we presented a stochastic model for job assignment. We proposed to make job assignment in VC fault tolerant by using a variant of the checkpointing strategy. Rather than saving the state of the computation, at regular times, the state of the computation is only recorded as needed. Also, since we do not assume a central server that stores checkpointed images, like conventional cloud providers do, in our strategy checkpointing is performed by a car and the resulting image is stored by the car itself. Once the car leaves, the image is lost. We consider two scenarios: in the first one, cars do not leave during checkpointing; in the second one, cars may leave during checkpointing, leading to system failure. Our main contribution is to offer theoretical predictions of the job execution time in both scenarios mentioned above. A comprehensive set of simulations have shown that our theoretical predictions are accurate

Trusted community : a novel multiagent organisation for open distributed systems

[no abstract

Volunteer computing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 205-216).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.This thesis presents the idea of volunteer computing, which allows high-performance parallel computing networks to be formed easily, quickly, and inexpensively by enabling ordinary Internet users to share their computers' idle processing power without needing expert help. In recent years, projects such as SETI@home have demonstrated the great potential power of volunteer computing. In this thesis, we identify volunteer computing's further potentials, and show how these can be achieved. We present the Bayanihan system for web-based volunteer computing. Using Java applets, Bayanihan enables users to volunteer their computers by simply visiting a web page. This makes it possible to set up parallel computing networks in a matter of minutes compared to the hours, days, or weeks required by traditional NOW and metacomputing systems. At the same time, Bayanihan provides a flexible object-oriented software framework that makes it easy for programmers to write various applications, and for researchers to address issues such as adaptive parallelism, fault-tolerance, and scalability. Using Bayanihan, we develop a general-purpose runtime system and APIs, and show how volunteer computing's usefulness extends beyond solving esoteric mathematical problems to other, more practical, master-worker applications such as image rendering, distributed web-crawling, genetic algorithms, parametric analysis, and Monte Carlo simulations. By presenting a new API using the bulk synchronous parallel (BSP) model, we further show that contrary to popular belief and practice, volunteer computing need not be limited to master-worker applications, but can be used for coarse-grain message-passing programs as well. Finally, we address the new problem of maintaining reliability in the presence of malicious volunteers. We present and analyze traditional techniques such as voting, and new ones such as spot-checking, encrypted computation, and periodic obfuscation. Then, we show how these can be integrated in a new idea called credibility-based fault-tolerance, which uses probability estimates to limit and direct the use of redundancy. We validate this new idea with parallel Monte Carlo simulations, and show how it can achieve error rates several orders-of-magnitude smaller than traditional voting for the same slowdown.by Luis F.G. Sarmenta.Ph.D

Shadow Banning in Browser-based Volunteering Computing

Browser-based volunteering computing projects are mainly used to perform scientific computations in heterogeneous clusters at a low cost. As for every community-driven approach, saboteurs can try to cheat the system for various reasons. In this paper, we propose to study whether such solutions could improve their performance and resilience by using shadow banning instead of a classic ban scheme. To do so, we have built a framework simulating a real system and studied the impact of shadow banning in relation with task types, saboteur rates, and detection techniques such as majority, m-first and credibility-based voting. Results show that shadow banning is overall more resilient, reducing the number of errors of detection by more than 33.5% in average. It also improves the server-side performance in a significant manner for saboteur rates between 0 and 20%

Contributions to Desktop Grid Computing : From High Throughput Computing to Data-Intensive Sciences on Hybrid Distributed Computing Infrastructures

Since the mid 90’s, Desktop Grid Computing - i.e the idea of using a large number of remote PCs distributed on the Internet to execute large parallel applications - has proved to be an efficient paradigm to provide a large computational power at the fraction of the cost of a dedicated computing infrastructure.This document presents my contributions over the last decade to broaden the scope of Desktop Grid Computing. My research has followed three different directions. The first direction has established new methods to observe and characterize Desktop Grid resources and developed experimental platforms to test and validate our approach in conditions close to reality. The second line of research has focused on integrating Desk- top Grids in e-science Grid infrastructure (e.g. EGI), which requires to address many challenges such as security, scheduling, quality of service, and more. The third direction has investigated how to support large-scale data management and data intensive applica- tions on such infrastructures, including support for the new and emerging data-oriented programming models.This manuscript not only reports on the scientific achievements and the technologies developed to support our objectives, but also on the international collaborations and projects I have been involved in, as well as the scientific mentoring which motivates my candidature for the Habilitation `a Diriger les Recherches

Knowledge Transfer Strategy Implementation in Contract Organizations

Despite economic perils of government shutdowns, foreclosures, bankruptcies, and employee layoffs, some contract leaders consistently fail to implement knowledge transfer strategies that could improve production and profitability and maintain operational readiness when employees transition in and out of the organization. The conceptual framework for this descriptive research study was Nonaka and Takeuchi\u27s socialization, externalization, combination, and internalization model for knowledge creation. A purposive sample of 20 leaders from 2 contract organizations within the south central United States with at least 10 years of experience in contracting were interviewed. Member checking was used for reliability of the synthesized interviews, and triangulation was accomplished by a review of the organization\u27s policies and standard operational procedures that confirmed the implemented processes. Thematic analysis was used to determine the 5 key themes identified in this study: cross-training, right-seat riding, after-action reviews, job shadowing, and surveying. By understanding the value of knowledge transfer strategy, business leaders and employees may benefit by establishing future business relationships and associations that create positive social change through established processes

Midlands Institute for Non-Profit Management: Building a Solid Foundation

Agenda and material from the Midlands Institute for Non-Profit Management - Building a Solid Foundation Conference, July 8-10, 1996

BitDew: A Programmable Environment for Large-Scale Data Management and Distribution

Desktop Grids use the computing, network and storage resources from idle desktop PC's distributed over multiple-LAN's or the Internet to compute a large variety of resource-demanding distributed applications. While these applications need to access, compute, store and circulate large volumes of data, little attention has been paid to data management in such large-scale, dynamic, heterogeneous, volatile and highly distributed Grids. In most cases, data management relies on ad-hoc solutions, and providing general approach is still a challenging issue. To address this problem, we propose the BitDew framework, a programmable environment for automatic and transparent data management on computational Desktop Grids. This paper describes the BitDew programming interface, its architecture, and the performance evaluation of its runtime components. BitDew relies on a specific set of meta-data to drive key data management operations, namely life cycle, distribution, placement, replication and fault-tolerance with a high level of abstraction. The Bitdew runtime environment is a flexible distributed service architecture that integrates modular P2P components such as DHT's for a distributed data catalog and collaborative transport protocols for data distribution. Through several examples, we describe how application programmers and Bitdew users can exploit Bitdew's features. The performance evaluation demonstrates that the high level of abstraction and transparency is obtained with a reasonable overhead, while offering the benefit of scalability, performance and fault tolerance with little programming cost